wechaty/go-wechaty

package puppetservice

import (
    "encoding/json"
    "fmt"
    "google.golang.org/grpc/resolver"
    "google.golang.org/grpc/resolver/manual"
    "io/ioutil"
    "net/http"
    "strings"
)

func wechatyResolver() resolver.Builder {
    r := manual.NewBuilderWithScheme("wechaty")
    r.BuildCallback = resolverBuildCallBack
    return r
}

func resolverBuildCallBack(target resolver.Target, conn resolver.ClientConn, options resolver.BuildOptions) {
    // target.URL.Host `api.chatie.io` in `wechaty://api.chatie.io/__token__`
    // target.URL.Path `__token__` in `wechaty://api.chatie.io/__token__`
    log.Trace("resolverBuildCallBack()")
    uri := fmt.Sprintf("https://%s/v0/hosties%s", target.URL.Host, target.URL.Path)
    address, err := discoverAPI(uri)
    if err != nil {
        conn.ReportError(err)
        return
    }
    if address == nil || address.Host == "" {
        conn.ReportError(fmt.Errorf(`token %s does not exist`, strings.TrimLeft(target.URL.Path, "/")))
        return
    }
    err = conn.UpdateState(resolver.State{
        Addresses: []resolver.Address{{
            Addr: fmt.Sprintf("%s:%d", address.Host, address.Port),
        }},
    })
    if err != nil {
        log.Error("resolverBuildCallBack UpdateState err: ", err.Error())
        return
    }
}

type serviceAddress struct {
    Host string
    Port int
}

func discoverAPI(uri string) (*serviceAddress, error) {
    response, err := http.Get(uri)
    if err != nil {
        return nil, fmt.Errorf("discoverAPI http.Get() %w", err)
    }
    defer response.Body.Close()

    // 4xx
    if response.StatusCode >= 400 && response.StatusCode < 500 {
        return nil, nil
    }

    // 2xx
    if response.StatusCode < 200 || response.StatusCode >= 300 {
        return nil, fmt.Errorf("discoverAPI http.Get() status:%s %w", response.Status, err)
    }
    data, err := ioutil.ReadAll(response.Body)
    if err != nil {
        return nil, fmt.Errorf("discoverAPI ioutil.ReadAll %w", err)
    }

    r := &serviceAddress{}
    if err := json.Unmarshal(data, r); err != nil {
        return nil, fmt.Errorf("discoverAPI json.Unmarshal %w", err)
    }
    return r, nil
}